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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Heiko Carstens <heiko.carstens@de.ibm.com>,
        Vasily Gorbik <gor@linux.ibm.com>
Subject: [PATCH 4.4 02/79] s390/topology: avoid firing events before kobjs are created
Date:   Wed, 16 Oct 2019 14:49:37 -0700
Message-Id: <20191016214732.696445726@linuxfoundation.org>
In-Reply-To: <20191016214729.758892904@linuxfoundation.org>
References: <20191016214729.758892904@linuxfoundation.org>
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From: Vasily Gorbik <gor@linux.ibm.com>

commit f3122a79a1b0a113d3aea748e0ec26f2cb2889de upstream.

arch_update_cpu_topology is first called from:
kernel_init_freeable->sched_init_smp->sched_init_domains

even before cpus has been registered in:
kernel_init_freeable->do_one_initcall->s390_smp_init

Do not trigger kobject_uevent change events until cpu devices are
actually created. Fixes the following kasan findings:

BUG: KASAN: global-out-of-bounds in kobject_uevent_env+0xb40/0xee0
Read of size 8 at addr 0000000000000020 by task swapper/0/1

BUG: KASAN: global-out-of-bounds in kobject_uevent_env+0xb36/0xee0
Read of size 8 at addr 0000000000000018 by task swapper/0/1

CPU: 0 PID: 1 Comm: swapper/0 Tainted: G    B
Hardware name: IBM 3906 M04 704 (LPAR)
Call Trace:
([<0000000143c6db7e>] show_stack+0x14e/0x1a8)
 [<0000000145956498>] dump_stack+0x1d0/0x218
 [<000000014429fb4c>] print_address_description+0x64/0x380
 [<000000014429f630>] __kasan_report+0x138/0x168
 [<0000000145960b96>] kobject_uevent_env+0xb36/0xee0
 [<0000000143c7c47c>] arch_update_cpu_topology+0x104/0x108
 [<0000000143df9e22>] sched_init_domains+0x62/0xe8
 [<000000014644c94a>] sched_init_smp+0x3a/0xc0
 [<0000000146433a20>] kernel_init_freeable+0x558/0x958
 [<000000014599002a>] kernel_init+0x22/0x160
 [<00000001459a71d4>] ret_from_fork+0x28/0x30
 [<00000001459a71dc>] kernel_thread_starter+0x0/0x10

Cc: stable@vger.kernel.org
Reviewed-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 arch/s390/kernel/topology.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/arch/s390/kernel/topology.c
+++ b/arch/s390/kernel/topology.c
@@ -291,7 +291,8 @@ int arch_update_cpu_topology(void)
 		topology_update_polarization_simple();
 	for_each_online_cpu(cpu) {
 		dev = get_cpu_device(cpu);
-		kobject_uevent(&dev->kobj, KOBJ_CHANGE);
+		if (dev)
+			kobject_uevent(&dev->kobj, KOBJ_CHANGE);
 	}
 	return rc;
 }